The micro-scanning mirror was first published in 1980, since then the micro-scanning mirror has become a considerably important research issue in the micro-opto-electromechanical system (MOEMS). The micro-scanning mirror is mainly applied in scanners, bar code scanners, laser printers, and projection display systems, etc.
Cathode ray tube televisions in the early stage are all belonged to the sequential scanning system. The operation principle is that the deflection direction of the electronic beam is controlled by the magnetic field under the vacuum environment. The electronic beam is radiated to the back side of the fluorescent screen, and the fluorescent powder is excited on the fluorescent screen so as to radiate the light. After the microelectromechanical system technology is developed, scanning mirrors by means of the light source projection are then developed continuously. The manufacturing methods of the scanning mirrors include the body-typed micro-manufacturing technology and face-typed micro-manufacturing technology.
There are many driving methods for the micro-scanning mirrors, and the electrostatic actuation and the thermal actuation the common ones, etc. However, due to the limited size, the micro-mirror actuated by the magnetism is generally ignored.
In fact, when the current direction is perpendicular to the magnetic field direction, Lorentz force appears. The micro-mirror can be controlled by Lorentz force.
Please refer to FIG. 1, which is a structural diagram showing a micro-mirror according to the prior art. In FIG. 1, the micro-mirror 1 manufactured from the silicon substrate in the etching technology can be layoutted with the copper conductor 3 by the micro-electroforming process. Then, two magnets (not shown in FIG. 1) are fabricated for providing the permanent magnetic field. When the current flows from the torsion bar 2 to the micro-mirror 1, Lorentz force can be generated by the interaction between the current and the magnetic field direction (MFD). Due to the current flowing through the torsion bar 2, the direction thereof is rotated. Therefore, the direction of the generated Lorentz force is also changed, which generates a torque to the micro-mirror 1. When the input signal is an alternating current, the micro-mirror will swing at a high speed. Since the driving source is the current, in order to decrease Joule heat generated on the conductor, the conductor must be plated thicker by means of the electroforming method so as to decrease the resistance of the conductor. In addition, due to the limitation in using the surface micromachining, the conductor cannot be produced as the cubic coil form. The conductor is usually laid out by the spiral method and the conductor is pulled out by the cubic crossing method, i.e. linked through the jumper 4.
However, two drawbacks exist in the traditional micro-mirror which utilizes Lorentz force. One is to produce the coil layout, which needs to spend the layout cost. The other is to avoid Joule heat generated when the large current flows through the coil. In addition, the two drawbacks can be cross-influenced. In order to avoid the generation of Joule heat, it is essential to increase the thickness of the conductor by the electroplating method. However, if the thickness of the layout is not enough, the conductor will be burned down by Joule heat when the current is too large. In order to correct the drawback of the prior art, the applicant of the present invention have applied the Taiwan Patent Application No. 095124215 on Jul. 3, 2006 (corresponding to the U.S. patent application Ser. No. 11/650,402 on Jan. 5, 2007 now published as U.S. Patent Application Publication No. 2008/0001680 A1) and the Taiwan Patent Application No. 096106288 on Feb. 16, 2007 (corresponding to the U.S. patent application Ser. No. 11/842,304 on Aug. 21, 2007 now published as U.S. Patent Application Publication No. 2008/0197951 A1). In these two patent applications, the magnetic element can be driven by Lorentz force and the magnetostatic force. In particular, the direction of the magnetostatic force is determined by controlling the strengths and/or relative locations and/or the magnetic-pole distribution of a plurality of magnetic field generating devices so as to determine the rotating status of the magnetic element. However, besides the abovementioned patent applications, it is therefore attempted by the applicant to deal with another magnetic element driven by applying Lorentz force and the manufacturing method therefor.